Lesson 18 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
Lesson 18 Objective: Measure an item twice using different length units and compare; relate measurement to unit size. Suggested Lesson Structure Fluency Practice 
Application Problem 
Concept Development 
Student Debrief 
(10 minutes) (5 minutes) (35 minutes) (10 minutes) (60 minutes) Total Time Fluency Practice (10 minutes)  Decomposition Tree 2.OA.2  Grade 2 Core Fluency Differentiated Practice Sets 2.OA.2 (5 minutes) (5 minutes) Decomposition Tree (5 minutes) Materials: (S) Decomposition Tree Template (from G2–M7–Lesson 6) Note: Students are given 90 seconds to decompose 20 inches. Students apply knowledge of sums and differences within 20 to length. T: (Distribute tree template.) T: You are going to break apart 20 incheson your Deco Tree for 90 seconds. Do as many problems as you can. Go! S: (Work for 90 seconds.) T: Now exchange your tree with your partner and check each other’s work. (Allow students 30–45 seconds to check.) T: Return each other’s papers. Did you see another way to make 20 inches on your partner’s paper? (Allow students to share for another 30 seconds.) T: Turn your paper over. Let’s break apart 20 inches for another minute. Grade 2 Core Fluency Differentiated Practice Sets (5 minutes) Materials: (S) Core Fluency Practice Sets from G2–M7–Lesson 1 Note: During G2–M7–Topic D and for the remainder of the year, each day’s fluency includes an opportunity Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
for review and mastery of the sums and differences with totals through 20 by means of the Core Fluency Practice Sets or Sprints. The process is detailed and Practice Sets provided in G2–M7–Lesson 1. Application Problem (5 minutes) Ezra is measuring things in his bedroom. He thinks his bed is about 2 yards. Is this a reasonable estimate? Explain your answer using pictures, words or numbers. Note: This Application Problem provides practice using benchmarks to estimate measurement. When students finish invite them to share their reasoning either whole group or with partners. Concept Development (35 minutes) Materials: (T) Chart for recording measurements as pictured below (S) Centimeter ruler, inch ruler; 1 plain sheet of white paper; bag with an unsharpened pencil, a new crayon, a new eraser Part 1: Compare centimeters and inches. Assign Partners A and B. T: Partner A, measure the pencil using the inch ruler. Partner B, measure the pencil using the centimeter ruler. T: Partner A, how long is the pencil? S: About 7 inches! T: (Record answer.) Partner B, how long is the pencil? S: About 18 centimeters! T: (Record answer.) Hmm, why do you think the measurements are so different? Turn and talk. S: We used different units to measure.  He measured MP.2 with an inch ruler, and I used a centimeter ruler. T: Are both measurements correct? S: Yes! T: Let’s check and see. Partner A, this time measure the pencil with the centimeter ruler. Partner B, measure the pencil with the inch ruler. S: (Measure.) T: Are your measurements the same as your partner’s when using the different rulers? S: Yes! Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org NOTES ON MULTIPLE MEANS OF ACTION AND EXPRESSION: Scaffold the lesson for English language learners by pointing to the inch ruler and the centimeter ruler while giving directions. Point out the different units on the rulers while asking students which unit is bigger: the inch or the centimeters. Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
T: Which is longer, a unit of one centimeter or one inch? S: An inch! T: That means 7 inches is about the same length as 18 centimeters. Did we use more centimeters or more inches to measure the pencil? S: More centimeters. T: Why did we need more centimeters to measure the pencil? S: Centimeters are smaller, so it takes more of them to cover the length of the pencil. T: Talk to your partner about why the measurements are different for the same object. S: Centimeters are smaller than inches.  It takes fewer inches to measure because inches are bigger.  The smaller the unit, the more units it takes to measure the same thing. Part 2: Measure using centimeters and inches. Give students time to measure both the objects in their bags and the sides of the white paper using both inches and centimeters. They should stop to record the measurements on the plain paper as they go. Encourage students to replicate your chart to organize their work. T: What pattern do you see in your measurements using the different rulers? S: The number of inches is always smaller.  The number of centimeters is always bigger, because a centimeter unit is smaller than an inch unit and it takes more of them when we are measuring. T: Does this remind you of the time we measured straws with two different size paper clips? S: Yes! T: Turn and talk: What do you know about measurement and unit size? NOTES ON S: The smaller the unit means it takes more of those units MULTIPLE MEANS OF when measuring something.  The bigger the unit ENGAGEMENT: means you use less of them. Support students performing below grade level by repeating the activity T: Using your rulers, draw two lines on your white paper. with different lengths. Ask them to Make one line 5 inches and the other 5 centimeters. draw lines that are 6 centimeters long T: Before you begin, tell your partner which line will be and 6 inches long. Repeat until longer. students are sure that the inch line is S: The 5 inch line! longer than the centimeter line and can explain that: T: Tell your partner how you know!  The same number of units will S: One inch is longer than 1 centimeter, so 5 inches will make a longer line when using be longer than 5 centimeters.  Inches are longer, so inches than centimeters. the line will be longer too.  It takes more centimeters than T: (Allow students time to draw the two lines.) inches to measure different T: Were we right? Is the 5‐inch line longer than the 5‐
objects. centimeter line? S: Yes! T: Look at your lines. How many centimeters do you think it would take to equal 5 inches? Use your centimeter ruler to check your estimate. Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
S: (Allow students time to check their estimate.) Thirteen centimeters is about 5 inches. T: Measure to see about how many inches 5 centimeters is. S: About 2 inches! T: How many centimeters would it take to be longer than 5 inches? Would you have to measure again or could you figure it out another way? S: We wouldn’t have to measure again because we know that 13 centimeters is about 5 inches, so to be longer than 5 inches, it can be any number of centimeters more than 13. Problem Set (10 minutes) Students should do their personal best to complete the Problem Set within the allotted 10 minutes. For some classes, it may be appropriate to modify the assignment by specifying which problems they work on first. Some problems do not specify a method for solving. Students solve these problems using the RDW approach used for Application Problems. Student Debrief (10 minutes) Lesson Objective: Measure an item twice using different length units and compare; relate measurement to unit size. The Student Debrief is intended to invite reflection and active processing of the total lesson experience. Invite students to review their solutions for the Problem Set. They should check work by comparing answers with a partner before going over answers as a class. Look for misconceptions or misunderstandings that can be addressed in the Debrief. Guide students in a conversation to debrief the Problem Set and process the lesson. You may choose to use any combination of the questions below to lead the discussion. 

Look at the lines you measured on your Problem Set. Talk to your partner about why it is important to label the length with your chosen unit. Why is it important to label our numbers in math in general? Look at Problem 5 on your Problem Set. Are the lines you drew equal in length? Why might Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM




somebody think that the lines should be equal? Can you think of other times where we have used different units in math? When you measured in centimeters and inches, did you ever have to round up or down? How did you do that? Talk to your partner about why the unit size matters when we are measuring things. Why do we measure using different units? When would you want to measure using a small unit? A large unit? Exit Ticket (3 minutes) After the Student Debrief, instruct students to complete the Exit Ticket. A review of their work will help you assess the students’ understanding of the concepts that were presented in the lesson today and plan more effectively for future lessons. You may read the questions aloud to the students. Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 Problem Set 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
Name
Date
Measure the lines in inches and centimeters. Round the measurements to the nearest
inch or centimeter.
1.
______ cm
______ in
______ cm
______ in
______ cm
______ in
______ cm
______ in
2.
3.
4.
Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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NYS COMMON CORE MATHEMATICS CURRICULUM
Lesson 18 Problem Set 2•7
5. Draw lines with the measurements below.
a. 3 centimeters long
b. 3 inches long
6.
a. Did you use more inches or more centimeters when measuring the lines above?
_______________________________
b. Write a sentence to explain why you used more of that unit.
____________________________________________________________
____________________________________________________________
7. Thomas and Chris both measured the crayon below but came up with different
answers. Explain why both answers are correct.
Thomas:
8
cm
Chris:
3
in
Explanation: ___________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 Exit Ticket 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
Name
Date
Measure the lines in inches and centimeters.
1.
______ cm
2.
______ in
__________________________________
______ cm
______ in
Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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Lesson 18 Homework 2•7
NYS COMMON CORE MATHEMATICS CURRICULUM
Name
Date
Measure the lines in inches and centimeters. Round the measurements to the nearest
inch or centimeter.
1.
_________________________________________________________
______ cm
2.
______ in
______________________________________
______ cm
3.
______ in
_____________________________
______ cm
4.
______ in
________________________________________________
______ cm
______ in
Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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NYS COMMON CORE MATHEMATICS CURRICULUM
Lesson 18 Homework 2•7
5. a. Draw a line that is 5 centimeters in length.
b. Draw a line that is 5 inches in length.
6. a. Draw a line that is 7 inches in length.
b. Draw a line that is 7 centimeters in length.
7. Takeesha drew a line 9 centimeters long. Damani drew a line 4 inches long.
Takeesha says her line is longer than Damani’s because 9 is greater than 4. Explain
why Takeesha might be wrong.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
8. Draw a line that is 9 centimeters long and a line that is 4 inches long to prove that
Takeesha is wrong.
Lesson 18: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Measure an item twice using different length units and compare; relate measurement to unit size. 4/17/14 This work is licensed under a Creative Commons Attribution‐NonCommercial‐ShareAlike 3.0 Unported License.
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